Question

我尝试通过将上传的流保存到位图中来处理ASP.NET中上传图像的大小，处理此位图并将处理后的位图保存到应保存到FTP文件夹的新流中。上传的流成功保存为位图并正确处理;只是新处理的流出现问题，导致图像损坏。以下是代码段：

        s = FileUpload1.FileContent;
        Bitmap bitmap = (Bitmap)Bitmap.FromStream(s);
        Bitmap newBmp = new Bitmap(250, 250, System.Drawing.Imaging.PixelFormat.Format24bppRgb);
        newBmp.SetResolution(72F, 72F);
        Graphics newGraphic = Graphics.FromImage(newBmp);
        newGraphic.Clear(Color.White);
        newGraphic.SmoothingMode = System.Drawing.Drawing2D.SmoothingMode.AntiAlias;
        newGraphic.InterpolationMode = System.Drawing.Drawing2D.InterpolationMode.HighQualityBicubic;
        newGraphic.DrawImage(bitmap, 0, 0, 250, 250);
        newBmp.Save(MapPath("temp.jpg"));
        Stream memoryStream = new MemoryStream();
        newBmp.Save(memoryStream, System.Drawing.Imaging.ImageFormat.Jpeg);

Answer 1

这里的关键是你得到一个空图像，这几乎总是一个从头开始不被读取的流。

在将位图写入后，您需要回到流的开头。

memoryStream.Seek(0, SeekOrigin.Begin); //go back to start

否则，当您稍后尝试保存该流时，它将从末尾读取流。当位图写入流时，它会附加字节，并使位置前进。以下是MVC中的示例代码。

<强> Index.cshtml

@{
    ViewBag.Title = "Index";
}

@using (Html.BeginForm("UploadImage", "BitmapConvert", FormMethod.Post, new { enctype = "multipart/form-data" })){
    <input type="file" name="uploadFile"/>

    <input type="submit" value="Upload"/>
}

<强> BitmapConvertController.cs

using System.Drawing;
using System.IO;
using System.Web;
using System.Web.Mvc;

namespace MvcSandbox.Controllers
{
    public class BitmapConvertController : Controller
    {
        public ActionResult Index()
        {
            return View();
        }

        [HttpPost]
        public ActionResult UploadImage(HttpPostedFileBase uploadFile)
        {
            var s = uploadFile.InputStream;

            var bitmap = new Bitmap(s);

            var resizedBitmap = new Bitmap(250, 250, System.Drawing.Imaging.PixelFormat.Format24bppRgb);
            resizedBitmap.SetResolution(72F, 72F);

            using (var g = Graphics.FromImage(resizedBitmap))
            {
                g.Clear(Color.White);
                g.SmoothingMode = System.Drawing.Drawing2D.SmoothingMode.AntiAlias;
                g.InterpolationMode = System.Drawing.Drawing2D.InterpolationMode.HighQualityBicubic;
                g.DrawImage(bitmap, 0, 0, 250, 250);

                resizedBitmap.Save("C:\\Test\\test.jpg", System.Drawing.Imaging.ImageFormat.Jpeg);

                using (var memoryStream = new MemoryStream())
                {
                    resizedBitmap.Save(memoryStream, System.Drawing.Imaging.ImageFormat.Jpeg);

                    using (var dest = new FileStream("C:\\Test\\stream.jpg", FileMode.OpenOrCreate))
                    {
                        memoryStream.Seek(0, SeekOrigin.Begin); //go back to start
                        memoryStream.CopyTo(dest);
                    }
                }

            }

            return RedirectToAction("Index");
        }
    }
}

将位图保存到流中

1 个答案: